Pathologic ocular neovascularization (NV) and related conditions occur as a cascade of events that progresses from an initiating stimulus to the formation of abnormal new capillaries. The stimulus appears to be the elaboration of various proangiogenic growth factors such as vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), and angiopoetins, among others. Following initiation of the angiogenic cascade, the capillary basement membrane and extracellular matrix are degraded and capillary endothelial cell proliferation and migration occur. Endothelial sprouts anastomose to form tubes with subsequent patent lumen formation. The new capillaries commonly have increased vascular permeability or leakiness due to immature barrier function, which can lead to tissue edema. Differentiation into a mature capillary is indicated by the presence of a continuous basement membrane and normal endothelial junctions between other endothelial cells and pericytes; however, this differentiation process is often impaired during pathologic conditions.
Retinal NV is observed in retinal ischemia, proliferative and nonproliferative diabetic retinopathy (PDR and NPDR, respectively), retinopathy of prematurity (ROP), central and branch retinal vein occlusion, and age-related macular degeneration (AMD). The retina includes choriocapillaries that form the choroid and are responsible for providing nourishment to the retina, Bruch's membrane that acts as a filter between the retinal pigment epithelium (RPE) and the choriocapillaries, and the RPE that secretes angiogenic and anti-angiogenic factors responsible for, among many other things, the growth and recession of blood vessels.
NV can include damage to Bruch's membrane which then allows growth factor to come in contact with the choriocapillaries and initiating the process of angiogenesis. The new capillaries can break through the RPE as well as Bruch's membrane to form a new vascular layer above the RPE. Leakage of the vascular layer leads to wet or exudative AMD and subsequent loss of cones and rods that are vital to vision.
Exudative AMD and PDR are the major causes of acquired blindness in developed countries and are characterized by pathologic posterior segment neovascularization (PSNV). The PSNV found in exudative AMD is characterized as pathologic choroidal NV, whereas PDR exhibits preretinal NV. In spite of the prevalence of PSNV, treatment strategies are few and palliative at best. Approved treatments for the PSNV in exudative AMD include laser photocoagulation and photodynamic therapy with VISUDYNE®; both therapies involve laser-induced occlusion of affected vasculature and are associated with localized laser-induced damage to the retina. For patients with PDR, grid or panretinal laser photocoagulation and surgical interventions, such as vitrectomy and removal of preretinal membranes, are the only options currently available. Several different compounds are being evaluated clinically for the pharmacologic treatment of PSNV, including RETAANE® (Alcon Research, Ltd.), Lucentis™, Avastin™ (Genentech), adPEDF (GenVec), squalamine (Genaera), CA4P (OxiGENE), VEGF trap (Regeneron), LY333531 (Lilly), and siRNAs targeting VEGF (CandS, Acuity) and VEGFR-1 (Sirna-027, Sirna Therapeutics). Lucentis™ (Genentech), an anti-VEGF antibody injected intravitreally, and Macugen™ (Eyetech/Pfizer), an anti-VEGF aptamer injected intravitreally, have recently been approved for such use.
Diabetes mellitus is characterized by persistent hyperglycemia that produces reversible and irreversible pathologic changes within the microvasculature of various organs. Diabetic retinopathy (DR) is a retinal microvascular disease that is manifested as a cascade of stages with increasing levels of severity and worsening prognoses for vision. Major risk factors reported for developing diabetic retinopathy include the duration of diabetes mellitus, quality of glycemic control, and presence of systemic hypertension. DR is broadly classified into 2 major clinical stages: nonproliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR), where the term “proliferative” refers to the presence of preretinal neovascularization as previously stated. Nonproliferative diabetic retinopathy (NPDR) and subsequent macular edema are associated, in part, with retinal ischemia that results from the retinal microvasculopathy induced by persistent hyperglycemia.
Neovascularization also occurs in a type of glaucoma called neovascular glaucoma in which increased intraocular pressure is caused by growth of connective tissue and new blood vessels upon the trabecular meshwork. Neovascular glaucoma is a form of secondary glaucoma caused by neovascularization in the chamber angle.
Tumor necrosis factor α (TNFα) is a major mediator of the inflammatory response, and has been implicated in many human diseases. Binding of TNFα to its cell surface receptor, TNF receptor-1 (TNFR1), activates a signaling cascase affecting a wide variety of cellular responses, including apoptosis and inflammation. TNFα is initially expressed as an inactive, membrane-bound precursor. Release of the active form of TNFα from the cell surface requires proteolytic processing of the precursor by TNFα converting enzyme (TACE/ADAM17) Inhibiting expression of TNFR1, TACE, or both will effectively reduce the action of TNFα. It has also been reported that TNFα is involved in neovascularization and endothelial cell function (Hangai et al., 2006, J. Neuroimmunol. 171:45-56; and Picchi et al., 2006, Circ. Res. 99:69-77). In addition, Kociok et al. demonstrated that TNFR1 deficient mice exhibited reduced angiogenesis in an oxygen-induced retinopathy model (Kociok et al., 2006, Invest. Ophthalmol. Vis. Sci. 47:5057-5065). In contrast, Vinores et al. observed reduced leukostasis but not reduced retinal neovascularization in response to oxygen-induced retinopathy in TNFR1 deficient mice relative to wild-type mice (Vinores et al., 2006, J. Neuroimmunol. 182:73-79). These studies indicated that TNFα is critical for ischemia-induced leukostasis, but not retinal neovascularization or VEGF-induced leakage. Thus, interfering with the TNFα pathway may selectively block pathological neovascularization without affecting the normal process.
The present invention addresses the above-cited ocular pathologies and provides compositions and methods using interfering RNAs that target TACE and/or TNFR1 for treating neovascularization associated with retinal edema, diabetic retinopathy, sequela associated with retinal ischemia, and posterior segment neovascularization, for example. U.S. Patent Publication 2005/0227935, published Oct. 13, 2005, to McSwiggen et al. relates to RNA interference mediated inhibition of TNF and TNF receptor gene expression. However, said publication teaches none of the particular target sequences for RNA interference as provided herein.